Spray painting system



@Wb 18, 1956 F. c. PARADISE; 2,763,5M

SPRAY PAINTING SYSTEM Filed Aug.. l2, l955 2 Sheets-Sheet l @W- 18, 1956F. c. PARADISE 763,53

SPRAY PAINTING SYSTEM Filed Aug. l2, 1953 2 Sheets-Sheet 2 SPRAY PAINTIGSYSTEM Francis C. Paradise, Libertyville, Ill., assgnor to Stewart-Warner Corporation, Chicago, Ill., a corporation of Virginia ApplicationAugust 12, 1953, Serial No. 373,722

3 Claims. (Cl. 299-86) The present invention relates to spray paintingsystems, and more particularly to the type of spray painting system inywhich the paint or other liquid material is fed to the spray gun by aliquid pump rather than from a tank placed under `air pressure.

One of the objects of the present invention is to provide an improvedspray painting system in which the liquid material is pumped directly tothe spray gun, and in `which the system, including the pressure in theliquid line, is completely under the control of the operator simplythrough manipulation of the trigger of the spray gun.

nited States Patent O An additional object is to provide a novel spraypainting system of the above type, in which there are specialarrangements to prevent surges of the liquid material when the spray isturned on and off by the 'operator through manipulation of the triggerat the spray gun.

Yet another object is to provide a novel system having the abovecharacteristics, land in which the liquid line to the spray gun is notunder pressure excepting during actual functioning of the `spray gun inapplying the paint or other liquid materia-l.

-another object is to provide a novel system of the type set out above,which prevents spurting of paint when the spray gun trigger is pulled.

Still another object is to accomplish the above at relatively low cost,by means of equipment which will function in a trouble-free manner.

Other objects will become apparent from the following description,reference being had to the accompanying drawings, in which Fig. l is adiagrammatic :representation of the system showing the paint tank andassociated mechanism, and

the connections between this mechanism and a spray gun; i

Fig. 2 is a vert-ical sectional View through a surge control valveincorporated in the mechanism of the present invention. The plane ofthis ligure is substantially parallel Ito the plane of Fig. 1 of thedrawings;

Fig. 3 is a vertical sectional View through the surge control mechanismillustrated in Fig. 2. The view of Fig. 3 is taken at substantiallyright angles to the view of Fig. 2;

Fig. 4 is an elevational view of a portion of the mechanism incorporatedin Fig. l, which serves the purpose of releasing the liquid pressure inthe -line to the spray gun when liquid under pressure at the gun is notneeded; and

Fig. 5 is a vertical sectional View through the device of Fig. 4, andmay be considered :as taken in the direction of the arrows substantiallyalong the line 5--5 of Fig. 4.

Spray painting systems are known in which the paint, lacquer, enamel, orother liquid, referred to generally hereafter as paint, is pumpeddirectly from a reservoir to the paint inlet connection of .the spraygun rather than being supplied to the spray gun from 1a reservoir keptunder an appropriate air pressure. The arrangement of pumping the paintdirectly to the spray gun 2,763,513 Patented Sept. 18, 1956 hasadvantages, but the use of such systems is usually accompanied by thedisadvantage that the sudden movement of paint through the hose line,accompanied by the sudden stoppage thereof, as the trigger ot the spraygun is -operated on and off, results in surges being imposed upon thesystem which are disconcerting and somewhat destructive of theequipment.

The lsystem of the present invention overcomes these disadvantages bypreventing surges in the paint line. In addition, when ordinary spraypainting equipment of the liquid pump type is used, release of the spraygun trigger leads to higher pressures at the paint connection to thespray g-un, with the result that there is likely to be some spurt-ing ofpaint when the operator next Worlcs the spray gun trigger. Thisdisadvantage is also overcome by the present invention.

Referring to Fig. l of the drawings, which shows a system in which thepresent invention is incorporated, a conventional spray gun is indicatedat 10, the spray gun being operated by working the customary trigger 12.Compressed air is supplied to the spray gun through a hose 14, while thepaint is brought to the gun by a hose 16. Compressed air lfor operatingthe equipment is supplied by way of a pipe yline or hose 18 which isconnected to the apparatus indicated generally at 2l). This apparatusmay conveniently be mounted upon and serve as the top for the paintreservoir 22.

Compressed air arriving at the equipment enters an automatic valve whichtor convenience will be referred to as the control valve. lt isindicated generally by the numeral 24. From the control valve, air issupplied to the hose 14 leading to the spray gun and to a pipe 26leading to a compressed air motor incorporated in a unit-ary structure28 which includes the motor and a paint pump driven thereby. Thecompressed `air motor and liquid pump may be conventional inconstruction, and therefore need no description. It is sufficient to'note that the pump driven by the compressed air motor withdraws iluidpaint by 'way of a pipe 30 leading into the reservoir 22 to a position`near the bottom thereof and forces the paint or other liquid outwardlythrough a connection 32 to a fluid pressure relief valve 34. From thisrelief valve the paint passes to the previously mentioned paint hose 16.There is also a paint return line 36 `leading from the pressure reliefvalve 34 back to the reservoir v22.

The pressure relief valve 34, actuated by a compressed air connectionrepresented by the hose 38, leads between the `control -valve and thepressure relief valve.

Referring now more specifically to the control valve which `.forms thesubject matter of Figs. 2 and 3, this device is formed of a cor-ed landmachined casting i0 to which another small casting, screw machine parts,and other valve elements are fitted. The main casting 40 has lan airinlet chamber 42 which contains a cylin drical screen element `i4 to thecenter of which air is admitted by `way of an air inlet lfitting 45.From the screen `44 the compressed air passes into a distributingchamber 46. This chamber is `formed :as a recess in one of the faces ofthe main casting 4d and `the `opening of this recess, which is generallycircular at the `face of the casting, is closed by 'a llexible diaphragm48 secured in place around its periphery by a cap Si). The main casting,the cap, `and the flexible diaphragm, are retained by several screws 52.

At its center, the diaphragm 48 is secured to a tting 54 which has apiloting stem 56 at the outer side of the diaphragm 48. This stem slideswithin a recess S3 formed in the cap 50 and maintains alignment of theparts. The diaphragm 43 and fitting 54 are biased away from the cap 50by a coil spring 60 which bears with one end against the fitting 54,while its opposed end is based against the cap 50.

The right-hand side of the diaphragm 48 as seen in Fig.

3, carries a poppet valve stem 62 threaded into the fitting 54, and thispoppet stem extends through a passage 64 leading from the recess 46 tothe atmosphere, The casting is so formed that valve seats 66 and 68,respectively, are formed at the inside and atmospheric ends of thepassage 64.

The valve stem 62 carries two poppet valves 70 and 72 for operationagainst the seats 66 and 68. Preferably, these valve poppets haveresilient faces and are so arranged that when the diaphragm 48 and valvestem 62 are moved toward the left, the outside valve poppet 70 will bebrought against the valve seat 68 at the atmospheric end of the passage64. When the diaphragm 48 and valve stem 62 are moved in the oppositedirection, that is, toward the right as seen in Fig. 3, the poppet 72will be brought against the valve seat 66 at the inner end of thepassage 64, thereby shutting off communication between this passage andthe air chamber 46.

It is apparent, therefore, that whenever the pressure in the chamber 46exceeds that in the space 74 between the diaphragm 48 and the cap 50 bya predetermined amount, the diaphragm 48 will move toward the left,thereby admitting air from the space 46 to the passage 64. On the otherhand, at some pressure differential when the pressures within the spaces46 and 74 are more nearly equal, the spring 60 will cause the diaphragm48 to move toward the right, thereby unseating the poppet 70 and closingpoppet 72. Under these conditions, communication is cut olf between thechamber 46 and the passage 64 and the passage 64 is vented to theatmosphere.

There is a passage 76 which intersects the passage 64 and leads to thepreviously mentioned control air line 38 attached to the pressure reliefvalve. This passage 76 also has a branch 78 which ends at a one-way balltype check valve 80 urged against a seat at the outlet end of thepassage 78 by a coil spring 82, this coil spring being retained in placeby a cap 84 threaded into the casting 40 in alignment with the passage78. The downstream side of the check valve 80 is in communication with acavity 86 which is connected to the pipe 26 which leads to the pumpmotor.

The previously mentioned air distribution chamber 46 also has an outletopening 88 which leads to a cylindrical chamber 90 connected to anoutlet passage 92 for attachment to the hose air line 14 leading to thespray gun. The opening 88 between the chambers 46 and 90 is flaredoutwardly at the top so as to provide a tapered valve seat 94 where itenters the chamber 90. A tapered valve plug 96 fits into this seat andis attached to a reciprocable valve stem 98, the upper end of whichextends through a hole 100 in a shallow cup 102 which is retained inplace by a threaded bushing 104. A coil spring 106 surrounds the valvestem 98 and bears with one end against the enlarged head at the plug 96.The opposite end of this spring bears v against a shoulder 108 at theupper end of a sleeve 110 ,which is slid over the valve stem 98. Thespring 106,

therefore, urges the sleeve 110 upwardly against the lower surface ofthe cup 102, whereas the opposite end of this spring urges the valve 96Yinto its seat so as to close the passage 88.

There is a vent passage 112 which extends from the recess 90 through ahole in the edge of the flexible diaphragm 48 and has its opposite endin communication with the chamber 74. This passage is for the purpose ofmaintaining the chamber 74 at the same pressure as the cavity 90.

The threaded bushing 104 which closes the exterior end of the cavity 90is formed to provide an inwardly facing cylindrical recess 114 whichcontains a piston 116 having a downwardly opening cavity 118 therein forthe purpose of clearing the upper end of the valve stem 98. Between theupper end of the piston 116 and the interior surface of the cap 104,there is a small soft acting coil spring 120 which urges the piston 116downwardly. The lower end of the piston 116 is reduced in diameterexternally so as to lit into a shallow cylindrical recess 122 in theupper face of the cup 102. Internally, the lower end of the piston 116is flared outwardly as indicated at 124, so as to provide a taperedspace for an annular row of steel balls 126 which surround the upperportion of the valve stem 98.

Downward movement of the piston 116 under the inlluence of the springbrings the tapered conical surface 124 at the lower yend of the pistonagainst the balls 126 and wedges them inwardly against the valve stem98. Because the spring 120 is comparatively soft in its action, however,the wedging action of the balls 126 against the valve stem is not greatenough to prevent the valve 98 from being seated under the influence ofthe spring 106.

There is a passage 128 which leads from the upper end of the cylinder114 at a position above the piston 116 to the cavity 86 upstream of theball check valve 80. The upper end of the piston 116, therefore, issubjected to whatever pressure prevails at the motor for the paint pump.

In addition to the above, the valve body 40 also contains a smallpassage 130 which connects the air distribution chamber 46 with thecavity 90 above the valve 96. As will appear presently, the purpose ofthis passage is to equalize ythe pressures in the chambers 90 and 46after a short time delay. The amount of the delay will depend upon thesize of the passage 130.

Referring now to the pressure relief valve illustrated in Figs. 4 and 5,it will be seen that this valve also is comprised of a cored andmachined casting with various tittings attached thereto and locatedtherein. At the lower end of this Valve structure there is a passagewhich extends therethrough for connection at one end to the outlet pipe32 from the paint pump. The opposite end of this passage is connected tothe hose 16 which supplies paint to the spray gun 10. Near its centerthe passage 140 intersects a vertically extending'cylindrical bore 142which is drilled into the valve body from the lower end. Within thisbore 142 there is an annular ring 144 retained against a shoulder nearthe upper end of the passage which is machined at its upper surface toprovide a seat for a valve ball 146. This seat forming member 144 issupported by a sleeve 148 which in turn is held in place by a cap 150threaded into the lower end of the bore 142. The sleeve 148 has a port152 through one side thereof in communication with the passage 140, andin order to orient the port 152 with the passage 140, the opposite sideof the sleeve 142 has a small opening 154 cut therethrough into whichthe end of a screw 156 projects. This screw, which is threaded throughthe main body casting,

' can also be removed to provide for the attachment of a .connection forflushing the interior paint passages of the valve 34.

The downstream side of the ball valve 146 is located within a chamber157 which communicates with the pipe 36 leading back to the paintreservoir 22. Thus', when the valve ball 146 is free to move, paint fromthe pump entering through the pipe 32 is free to pass upwardly aroundthe ball valve 146 and back to the paint reservoir by wayof the pipe 36.Under these conditions, there is substantially no pressure in the painthose 16.

Directly above the valve ball 146 there is a plunger 153 the upper endof which is attached to a piston 160 which tits within a pneumaticcylinder 162 provided within a cap 164 threaded at 166 to the maincasting. This pneumatic .cylinder 162 isI in communication through thetop center thereof with the hose 38 which leads to the control valve.Normally the piston 160 and plunger 158 vare urged upwardly by a coilspring 168 which bears against the lower surface of the piston at oneend, with its opposite end based in an annular groove 170 formed withinthe upper surface of the main body casting. So as to prevent paint fromleaking into the pneumatic cylinder, a ring of packings 172 is providedaround the plunger 1 ,58'at the upper end of the recess 157, and isretained in place by a packing nut 174 which is slid over the plunger158 and threaded into the top surface of the main body casting at thecenter thereof.

With the elements of the system connected as shown and described, theapparatus `operates in the following manner.

When compressed air is supplied to the line 18, it passes through thescreen 44 into the distribution chamber 46. This pressure operatingagainst the end of the valve 96 will raise it off its seat so that aircan ow into the chamber 9i) and fill the hose line 14 to the spray gun.The valve 96 will soon seat, however, because if the trigger at thespray gun is in the released position air cannot flow from the hose line14 and therefore the air fiowing around the valve 96 and that liowingthrough the bypass 130 will soon equalize the pressures in the chambers46 and 90.

Inasmuch as the chamber 90 is in communication with the chamber 74 atthe left side of the diaphragm 48, the pressures on the two sides ofthis diaphragm will balance and poppet 72 will be held against its seat66 by the spring 60. Therefore, air cannot flow to the passage 64. Noair pressure is imposed upon the upper surface of the pneumatic piston16u, nor does air pass through the line 26 to the pump motor. The systemtherefore comes to rest with only the air line to the spray gun 10 beingunder pressure.

If. now, the trigger is pulled by the operator, air will flow throughthe hose 14 and from the spray gun 1t). This drops the pressure withinthe chamber 90 and causes the valve plug 96 to move upwardly inasmuch asthe air capacity of the spray gun is far greater than that of thepassage 130. The pressure developed by the spring 106 is such that withair flowing from the chamber 46 to the hose line 1 4 around the valveplug 96, the restriction offered by this valve will be enough so thatthe pressure in the chamber 9i) will be about 7 p. s. i. less than it isin the chamber 46. This causes the pressure in the diaphragm chamber '74to be about 7 p. s, i. less than in the chamber 46, because of thecommunication provided by the passage 112.

Under this pressure differential, the diaphragm 48 moves toward theleft, thereby closing the valve poppet 7i) against its seat and movingthe valve poppet 72 toward the left as seen in Fig. 3, therebypermitting air to enter the passage 64 and by way of pass-age 76 toarrive at the line 33 leading to the pneumatic cylinder 162. Theincrease in pressure in the pneumatic cylinder 162 forces the piston 160and plunger 158 downwardly, thereby clamping the valve ball 146 tightlyagainst its seat so as to shut off the reservoir return line 36 fromcommunication with the paint pump outlet.

Simultaneously, air passes upwardly from the passage 76 around the ballcheck valve Sil to the chamber 86, and thence to the motor for the paintpump. The pump `therefore starts operating and passes paint from thereservoir through the passage 14@ of the valve 34 to the paint line 16and thence to the spray gun 1i). Under these circumstances the customaryspray pattern is produced by the spray gun lil, since both paint and airare supplied thereto at the appropriate pressures.

As soon as air reaches the chamber 36 above the ball valve 80, thispressure is communicated by way of the passage 128 to the upper end ofthe piston 116, thereby forcing this piston downwardly so as to Wedgethe balls 126 inwardly against the stem 9S of the valve 96. Thistherefore locks the valve 96 in the open position and prevents hunting,or other unevenness in flow therethrough, and also provides a closingtime delay as will appear presently.

The system continues in operation in the fashion just described untilthe trigger 12 is released. As soon as this happens, flow will ceasethrough the air line 14, thereby permitting the pressure in the chamber90 to rise to the level of that in the chamber 46 almost instantly. Thiscauses the pressure in the diaphragm chamber 74 to rise similarly andthus the spring 60 urges the diaphragm 48 and valve stem 62 toward theright, as seen in Fig. 3. This closes poppet valve 72 and opens poppet70.

Air, therefore, ceases to iiow to the pump motor or to the control line3S leading to the pneumatic cylinder 162. Opening of the poppet 7l)immediately drops the pressure of the control connection 38 to thepneumatic cylinder to atmospheric, thereby permitting the piston 160 andplunger 158 to rise with the result that the pressure in the paint hose16 leading to the gun, and the pressure at the pump outlet, that is, thepipe 32, immediately drops to atmospheric or thereabouts inasmuch as thepassage 140 is now freely in communication with the line 36 leading backto the reservoir.

It should be noted that whereas the pressure in the passage 76, andtherefore the pressure at the pneumatic cylinder 162, drops toatmospheric immediately, there is some delay in the pressure drop withinthe chamber 86 leading to the pump motor, because the ball check valveprevents reverse flow from the pump rnotor through `the passage 78. Thepump motor therefore will `run for a very brief interval. During thisinterval, or a portion thereof, the piston 116 will be held downwardlybecause of the communication between the piston cylinder 114 and thechamber 86 afforded by the passage 128. The valve plug 96 is thereforemomentarily locked in its open position.

The result of this is that if the operator releases the trigger 12 onlyfor an instant, as often happens, the pump motor and pump will continuein operation, and the valve 96 will remain open. However, since thepneumatic cylinder 162 operates almost instantly, the pressure in thepaint line to the gun will drop somewhat before the trigger 12 is againactuated. This has the advantage of preventing spurting of paint fromthe spray gun when the trigger is again pulled.

The system, therefore, automatically turns on the pump and its motorwhich supplies paint to the spray gun whenever the trigger 12 is pulled,and shuts off the pump motor and relieves the pressure in the paint lineto the gun almost instantly Whenever the trigger 12 is released for anappreciable interval of time. If the trigger is released onlymomentarily, the pressure in the paint line drops somewhat so as toprevent spurting, but the pump motor continues in operation during thisshort interval.

While I have shown and described a preferred embodiment of my invention,it will be apparent that numerous variations and modifications thereofmay be made without departing from the underlying principles of theinvention. I therefore desire, by the following claims, to includewithin the scope of the invention all such variations and modificationsby which substantially the results of my invention may be obtainedthrough the use of substantially the same or equivalent means.

I claim:

' l. A liquid supply system for use with a paint spray gun comprising,an air fitting for connection to said gun, a liquid fitting forconnection to said gun, a compressed air motor, a liquid pump driven bysaid motor, a liquid reservoir, said pump being connected forwithdrawing liquid from said reservoir and supplying said liquid underpressure to said liquid fitting when said motor receives air underpressure, means forming a bypass between said liquid fitting and saidreservoir, a valve in said bypass, pressure responsive means for closingsaid by--pass valve when said pressure responsive means is supplied withair under pressure, means forming a chamber having an air inletconnection for supplying air thereto, said chamber having a first outletpassage leading to said air fitting and a second outlet passage leadingto said pressure responsive means, a resiliently loaded valve in saidfirst outlet passage, the last said valve being oriented to be opened byflow from said chamber to said air fitting and being adapted to restrictsaid flow to produce a pressure differential across the last said valvewhen air is flowing from said air fitting,

means forming a restricted bypass around said resiliently loaded valvefor slowly equalizing the pressure on the two sides of the last saidvalve when the last said valve is closed, a pressure differentialactuated two-position valve in said second outlet passage, saidtwo-position valve being adapted when subjected to pressure differentialto open to connect said chamber to said pressure responsive means andwhen not subjected to `a pressure differential to close said secondoutlet passage and to vent said pressure responsive means to theatmosphere, means for imposing said pressure differential on saidpressure differential actuated valve, means forming a connection fromsaid pressure responsive means to said air motor, a check valve in thelast said connection, said check valve being oriented to permit flow tosaid air motor `and to prevent fiow in the opposite direction, pressureactuated means for clamping said resiliently loaded valve to preventmovement thereof, and means for subjecting said pressure actuated meansto the pressure prevailing at said air motor.

2. A liquid supply system for use with a paint spray gun comprising, anair fitting for connection to said gun, a liquid fitting for connectionto said gun, a compressed air motor, a liquid pump driven by said motor,a liquid reservoir, said pump being connected for withdrawing liquidfrom said reservoir and supplying said liquid under pressure to saidliquid fitting when said motor receives air under pressure, meansforming a bypass between said liquid fitting and said reservoir, a valvein said bypass, pressure responsive means for closing said bypass valvewhen said pressure responsive means is supplied with air under pressure,means forming a chamber having an air inlet connection for supplying airthereto, said chamber having a first outlet passage leading to said airfitting and a second outlet passage leading to said pressure responsivemeans, a resiliently loaded valve in said first outlet passage, thellastsaid valve being oriented to be opened by fiow from said chamber to saidair fitting and being adapted to restrict said fiow to produce apressure differential across the last said valve when air is fiowingfrom said air fitting, a pressure differential actuated twopositionvalve in said second outlet passage, said twoposition valve beingadapted when subjected to a pressure differential to open to connectsaid chamber to said pressure responsive means `and when not subjectedto a pressure differential to close said second outlet passage and tovent said pressure responsive means to the atmosphere,

means for imposing said pressure differential on said pressuredifferential actuated valve, means forming a connection from saidpressure responsive means to said air motor, a check valve in the lastsaid connection, said check valve being oriented to permit flow to saidairfmotor and to prevent fiow in the opposite direction, pressureactuated means for clamping said resiliently loaded valve to preventmovement thereof, and means for subjecting said pressure actuated meansto the pressure prevailing at said air motor. l

3. A liquid supply system for use with a paint spray gun comprising, anair fitting for connection to said gun, a liquid fitting for connectionto said gun, means for supplying liquid under pressure to said liquidfitting when said means receives air under pressure, means forming a lowpressure outlet for said liquid fitting, a valve in said outlet,pressure responsive means for closing said valve when said pressureresponsive means is supplied with air under pressure, means forming achamber having an air inlet connection for supplying air thereto, saidchamber having a first outlet passage leading to said air fitting and asecond oulet passage leading to said pressure responsive means, a

resiliently loaded valve in said first outlet passage, the last saidvalve being oriented to be opened by flow from said chamber to said airfitting and being adapted to restrict said fiow to produce a pressuredifferential across the last said valve when air is fiowing from saidair fitting, a pressure differential actuated two-position valve in saidsecond outlet passage, said two-position valve being adapted whensubjected to a pressure differential to open to connect said chamber tosaid pressure responsive means and when not subjected to a pressuredifferential to close said second outlet passage and to vent saidpressure responsive means to the atmosphere, means for imposing saidpressure differential on said pressure differenti-al actuated valve,means forming a connection from said pressure responsive means to saidliquid supplying means, a check valve in the last said connection, saidcheck valve being oriented to permit fiow to said liquid supplying meansand to prevent fiow in the opposite direction, pressure actuated meansfor clamping said resiliently loaded valve to prevent movement thereof,and means for subjecting said pressure actuated means to the pressureprevailing at said liquid supplying means.

4. A liquid supply system for use with a paint spray gun comprising, anair fitting for connection lto said gun, a liquid fitting for connection'to said gun, means for supplying liquid under pressure 'to said liquidfitting when said means receives air under pressure, means forming aflow pressure outlet for said liquid fitting, a valve in said outlet,pressure responsive means for closing said valve Iwhen said pressureresponsive means is supplied with air under pressure, means forming achamber having an air inlet connection for supplying air thereto, saidchamber having a first outlet passage leading to said air `fitting and asecond outlet passage leading to said pressure responsive means, aresilien-tly loaded valve in said first youtlet passage, the last saidvalve being oriented to be opened by ffow from said chamber to said airfitting and being adapted to restrict said flow to produce -a pressuredifferential vacross the llast said valve when air is fiowing from saidair fitting, means 'forming a restricted |`bypass around saidresiliently loaded valve `for slowly equalizing the pressure on `the twosides `of the last said valve when the last said valve is closed, apressure differential actuated 'two-position valve in said second outletpassage, said ytwo-position valve being adapted when subjected topressure differential to open to connect said chamber to said pressureresponsive means and when not subjected to a pressure differenti-al toclose said second outlet passage and to vent said pressure responsivemeans to the atmosphere, means for imposing said pressure differentialon said pressure differential actuated valve, means forming a connectionfrom said pressure responsive means to said liquid supplying means, acheck valve in the last said connection, said check valve being oriented'to permit ow to said liquid supplying Imeans and to prevent fiow inlthe opposite direction, pressure actuated means for clamping saidresiliently loaded valve to prevent movement thereof, and means lforsubjecting said pressure |actuated means to the pressure prev-ailing a-tsaid liquid supplying me-ans.

5. A liquid supply system for use with a paint spray gun having 1an lairsupply line and .a liquid supply line comprising, means for supplyingliquid under pressure to said liquid `supply line when said meansreceives air under pressure, means forming a low pressure outlet forsaid liquid supply line, a valve -for closing said outlet, pressureresponsive means for closing said valve when said pressure responsivemeans is supplied with air under pressure, means forming a chamberhaving -an air inlet connection, said chamber having a first outletpassage `lea-ding to said air supply line and a second outlet passageleading to said pressure responsive means, means 4to produce a pressuredifferential when -air is fiowing to said air supply line, a pressuredifferential actuated two-position valve in said second outlet passage,said two-position valve being ladapted when subjected to a pressuredifferential Ito open to connect said chamber to said pressureresponsive means and when not subjected to a pressure differential toclose said second outlet passage and to vent said pressure responsivemeans to the atmosphere, means for imposing said pressure differentialon said pressure differential actuated valve, means forming an airsupply connection between said second outlet passage and said liquidsupplying means, and check valve means interposed in said air supplyconnection Ito prevent the reverse flow of air past the check valveIfrom said liquid supplying means thus providing for limited continued`operation of the latter by air held against return `flow through `thecheck valve `after the air supply has been terminated by operation ofsaid two-position valve.

6. A liquid supply system for use with a paint spray `gun `having an airsupply line and a liquid supply line comprising, means 'for supplyingfliquid under pressure to said liquid supply line when said meansreceives air under pressure, means forming a low pressure outlet forsaid liquid supply line, a valve for closing said outlet, pressureresponsive means for closing said valve when said pressure responsivemeans is supplied with air under pressure, means forming a chamberhaving an `air inlet connection, said chamber having an outlet passageleading to said pressure responsive means, air supply means connected tosaid air supply line, -means in said air supply means for producing asubstantial pressure diierential therein as an incident to the flow ofair therethrough to said air supply line, a pressure differentialactuated two-position valve in said outlet passage, said two-positionvalve being adapted when subjected to a pressure differential to open toconnect said chamber lto said pressure responsive means and when not`subjected lto a pressure diierential to close said `outlet passage andto vent said pressure responsive means to the atmosphere, means forimposing said pressure differential of said air supply means on saidpressure dilerential actuated valve, means forming an air supplyconnection between said outlet passage and said liquid supplying means,and check valve means interposed in said air supply connection `toprevent the reverse iiow of air past the check valve from said liquidsupplying means, thus providing for limited continued operation of thelatter by air held against return flow lthrough the check v-alve afterthe air supply has been terminated by loperation of said two-positionvalve.

7. For use with 1a spray gun having separate air and liquid `supplyinlets, an air and liquid supply system comprising, in combination, pumpmeans for supplying liquid under pressure, means adapted to connect theoutiet of the pump means Yto ythe liquid supply inlet of a spray gun,uid pressure control means `connected with 'the outlet of the pump Itounload the liquid output pressure therefrom in response to ya criticalchange in the pressure of a controlling iluid medium supplied to thecontrol means, means for supplying air under pressure to said pressureresponsive pump outlet control means and including a valve operable tosharply change the pressure cf air [applied to said pump loutletcontrol, -an operator for said valve formed for actuation by dilerentialuid pressure applied thereto, means adapted to supply air under pressureto the air inlet of the spray gun and including a flow orifice therein,a `flow restriction member movably disposed adjacent the downstream sideof said orifice, biasing means acting on said ilow restriction member tourge the latter toward closing relation with said orifice, the biasingmeans yielding to reduce the restrictive effect of the liow restrictionmember to permit Widely varying rates of iiuid flow through the orificewhile providing for a relatively stabilized diierential pressure onIopposite sides of the oriiice for the different flow rates, and meansconnecting the diiferentia'l fluid pressure on opposite sides of theorifice tothe diterential iluid pressure valve yoperating means.

8. For use with a spray gun having separate -air and liquid supplyinlets, an air and liquid supply system comprising, in combination, pumpmeans for supplying liquid under pressure, -means adapted to connect theoutlet `of the pump means to the liquid supply inlet of a spray gun, uidpressure con-trol means connected with the outlet of the pump -to unloadthe liquid output pressure therefrom in response to a critical change inthe pressure of a controlling fluid medium supplied to the controlmeans, means for supplying air under pressure to said pressureresponsive pump outlet control means and including a valve operable tosharply change the pressure of air applied Ito said pump outlet controlmeans, an operator for said valve formed for actuation Iby differential'liuid pressure `applied thereto, means adapted `to supply air underpressure to the air inlet of the spray gun and including an orificetherein, a ow restriction member movably disposed adjacent thedownstream side of said orifice, biasing means Iacting on said iiowrestriction member to urge the latter toward closing relation with saidoriiice the biasing means yielding to reduce the restrictive efect ofthe flow restriction member to permit widely differing rates of air iiowthrough the orifice While providing for a relatively stabilizeddiierential pressure on Iopposite sides of fthe orice for 4the dilerent:dow rates, means connecting the diierential iiuid pressure on oppositesides of the orifice tothe dierential fluid pressure valve `operatingmeans, and fluid pressure actuated retaining means communicating withthe downstream side of said valve land mechanically connected with saidow restriction member to temporarily hold the latter away from saidorifice against the lforce of said biasing means when fluid ow throughsaid valve is momentarily interrupted.

References Cited in the ile of this patent UNITED STATES PATENTS

